[Talk-ca] GeoBase Import - Where we stand now

Michel Gilbert michcasa at gmail.com
Sun Dec 7 00:15:28 GMT 2008


2008/12/6 Steve Singer <ssinger_pg at sympatico.ca>

> On Sat, 6 Dec 2008, Michel Gilbert wrote:
>
>  I need some clarification about the parallel database (PostGIS). I am sure
>> I
>> see the whole picture of the Geobase Import process. Who is going to host
>> the change tracking PostGIS database ? How are we going to access it ? I
>> prefer a process model that uses only osm database. I don't see how we are
>> going to maintain the PostGis database for users that access Potlatch or
>> JOSM. May be I have not understood the concept yet.
>>
>
> I was thinking that the spatial database would only be used to generate the
> mappings between the OSM and geobase nodes.  Once a OSM node was deemed to
> be a geobase node the live OSM database would be updated to contain the
> geobase_nid tag.  You wouldn't keep the PostGIS database around, after the
> initial mapping process has done you will be able to get the 'mappings' from
> the OSM database by examining everything with a geobase_nid tag.
>
> PostGIS was only an example platform for generating automated mappings, you
> could probably do this in a JOSM plugin (that reads geobase files) and has
> geometric routines for determine if two lines a essentially the same.
>

Ok. I do not mind to work with spatial database such as PostGIS if it is
needed for the import. However when i have done some tests to import Geobase
data into osm I did not use intermidiate storage. Here's what i have done:

   1. Read osm data (bounding box)
   2. Read Geobase data in shape file (same bounding box)
   3. Reproject in LCC (it is easier to manipulate data in x,y coordinates)
   4. Compare both sources to identify Geobase segments that will be import
   5. Tag Geobase segment as osm ways
   6. Integrate the geobase to osm ways:
      1. snap geobase ways to osm ways (add nodes to existing osm way)
   7. Reproject to geographic coordinates
   8. Generate osm nodes:
      1. existing osm nodes
      2. new nodes added to existing osm way (geobase snapped)
      3. new nodes for geobase segments
   9. Generate osm ways to include new osm nodes
   10. Generate new osm ways that came from geobase
   11. Generate osm file
   12. Then use JOSM to upload the update file



>
>
>  Did we figure out the development platform ? The basic script to map the
>> road classes are written to work with JOSM ? or could it be something
>> else.
>> I work with FME (Safe Software) a canadian company in BC. It is a great
>> ETL
>> (Extract,Transform,Load) application. I know it is a commercial product
>> but
>> it could help for the task we have. FME read osm and PostGIS formats and
>> offers many tools to find change detections and manipulate attributes and
>> geometry. FME has a large community, may be even among osm. It could be
>> interesting to find out.
>>
>
> This is still open.  A lot depends on how much manual intervention is
> required in the process.  If the process can be automated then I think we'd
> want scripts that can be run in a batch fashion (so not a JOSM plugin) but
> if each tile is going to need a fair amount of manual massaging then a JOSM
> plugin is more appealing.
>
> We also have to consider what people are willing and able to develop in.  I
> wouldn't exclude FME on the basis that it is commercial it does restrict the
> pool of developers that could help with any scripting (and might have
> implications on where/how the import gets run)


Good. I am familiar fme. If i participate in the import I'll try to make
generic fme workbenches so they'll be sharable among participants.


>
>
>> Michel
>>
>>
>
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